JP2002353395A - Lead frame manufacturing method, lead frame, and semiconductor device - Google Patents

Abstract

(57) [Problem] To provide a lead frame manufacturing method, a lead frame, and a semiconductor device that do not cause distortion in a lead frame even when a die pad is thinned by coining. SOLUTION: A lead 12, a die pad 13, and a plurality of support bars 11 integrated with the die pad 13.
And a dividing step of dividing the die pad 13 formed integrally with the support bar 11 into a plurality of separated die pads 13 by dividing the die pad 13 for each of the support bars 11. And a coining step of, after the dividing step, performing a coining process on at least one main surface 13c of each of the plurality of die pads 13 to make the plurality of die pads 13 thin. It depends on the method of manufacturing the frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a lead frame, a lead frame, and a semiconductor device.

[0002]

2. Description of the Related Art With the recent miniaturization of electronic devices, there is a demand for miniaturization of semiconductor devices mounted on the electronic devices. 2. Description of the Related Art There are various types of semiconductor devices, and one that has been used from the past includes a semiconductor device mounted on a lead frame. FIG. 5A shows a cross section of the semiconductor device according to the conventional example.

As shown in FIG. 1, in a conventional semiconductor device 30, a semiconductor element 34 is fixed on a die pad 31a of a lead frame 31.
The electrode terminals 4 (not shown) and the leads 31 b of the lead frame 31 are wire-bonded via bonding wires 32. In the figure, reference numeral 33 denotes a sealing body for sealing the semiconductor element 34 and the bonding wires 32.

[0004] As shown in the figure, the lead 31b of the lead frame 31 only slightly projects from the outer periphery of the sealing body 33 without being bent into a gull-wing shape. A semiconductor device provided with such leads 31b is called a QFN (Quad Flat Non-lead) type semiconductor device. In a QFN type semiconductor device,
As described above, since the lead is not bent into a gull-wing shape and does not protrude significantly outside, the size can be made close to the size of the semiconductor element.

[0005]

In the semiconductor device 30, the back surface of the die pad 31a, that is, the surface on which the semiconductor element 34 is not fixed is exposed outside without being sealed. This structure has the advantage that the heat generated in the semiconductor element 34 is efficiently radiated to the outside, while moisture penetrates between the die pad 31a and the sealing body 33, and the semiconductor element 34 functions as desired by the moisture. May be lost. In addition, when the die pad 31a touches a terminal portion of a mounting substrate such as a motherboard, the terminal portions are short-circuited. Therefore, the mounting substrate must be designed so that the terminal portion does not come under the die pad 31a.
This causes a disadvantage that the design of the mounting board must be limited.

In order to avoid these disadvantages, a semiconductor device shown in FIG. 5B has been proposed. In this semiconductor device 35, the die pad 31a is lifted upward by bending a support bar (not shown), and the sealing body 33 is turned around to the back surface of the die pad 31a so that the die pad 31a is not exposed to the outside. ing. However, with this structure, there is a new inconvenience that the thickness t of the semiconductor device 35 is increased by the bending depth of the support bar.

To avoid this inconvenience, FIG.
A semiconductor device shown in (c) has been proposed. In this semiconductor device 36, instead of bending the support bar, the back surface of the die pad 31 a is subjected to half etching to make the die pad 31 a thin, and the back surface is sealed with a sealing body 33.
By this, the die pad 31a is not exposed to the outside. However, since half-etching is generally expensive, applying such half-etching causes a further problem of increasing the manufacturing cost of the semiconductor device.

Therefore, it is conceivable to reduce the thickness of the die pad 31a by coining instead of half etching. However, in the coining process, since the material is stretched by an amount corresponding to the reduced thickness, if a wide area such as the die pad 31a is coined, the extent of the stretching becomes extremely large, causing a further problem that the entire lead frame is distorted. .

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the related art, and a lead frame manufacturing method, a lead frame, and a lead frame which do not generate distortion even when a die pad is thinned by coining. It is an object to provide a semiconductor device.

[0010]

The first object of the present invention is to provide a process for forming a lead, a die pad, and a plurality of support bars integrated with the die pad on a metal strip. A dividing step of dividing the die pad integrated with the support bar into a plurality of die pads separated from each other by dividing the support bar into a plurality of die pads separated from each other; A coining step of subjecting at least one main surface to coining to reduce the thickness of the plurality of die pads.

Another object of the present invention is to provide a method for manufacturing a lead frame according to the first invention, wherein the processing step and the dividing step are simultaneously performed. Or, in the dividing step of the third invention,
The first invention or the first invention, wherein the shape of each of the plurality of die pads is roughly divided into a rectangle, and one of the two diagonals of the rectangle is on a virtual extension of the support bar. According to a second aspect of the invention, there is provided a method for manufacturing a lead frame.

In a fourth aspect of the present invention, in the dividing step, the shape of each of the plurality of die pads is divided into substantially right triangles, and one of two sides sandwiching a right angle of the right triangle is formed. According to a first aspect of the present invention, there is provided a method for manufacturing a lead frame, the method being provided on a virtual extension of the support bar. Or
A lead frame manufactured by the lead frame manufacturing method according to any one of the first to fourth inventions, which is a fifth invention, and a lead frame opposite to a main surface of the plurality of die pads. A semiconductor comprising: a fixed semiconductor element; a bonding wire for electrically connecting an electrode terminal of the semiconductor element to the lead; and a sealing body for sealing at least a main surface of the die pad. Settle by device.

According to a sixth aspect of the present invention, there is provided a lead, a die pad divided into a plurality of pieces, and a plurality of support bars integrated with each of the divided die pads. The problem is solved by a lead frame characterized by being thinner than the bar. Alternatively, in the seventh invention, the shape of each of the plurality of die pads is substantially rectangular, and one of two diagonals of the rectangle is on a virtual extension of the support bar. According to a sixth aspect of the present invention, there is provided a lead frame.

According to an eighth aspect of the present invention, the shape of each of the plurality of die pads is a substantially right triangle, and one of two sides sandwiching a right angle of the right triangle substantially corresponds to the support bar. The sixth feature is on a virtual extension.
The invention is solved by the lead frame according to the invention. Next, the operation of the present invention will be described.

According to the lead frame manufacturing method of the present invention, in the processing step, the lead, the die pad,
A plurality of support bars integrated with the die pad are formed on a metal strip. Thereafter, in a dividing step, the die pad integrated with the support bar is divided into a plurality of die pads separated from each other by dividing the die pad into the support bars. Thereafter, in the coining step, at least one main surface of each of the plurality of die pads is subjected to coining to reduce the thickness of the plurality of die pads.

In the coining process, the material is stretched by an amount corresponding to the thinning. However, in the present invention, the die pad is divided into a plurality of pieces and separated from each other in the dividing step. However, since the extension of the die pad is released to the space between the die pads, no distortion occurs in the lead frame.

Further, when the above-described processing step and the dividing step are performed simultaneously, there is an advantage that the manufacturing process of the lead frame is shortened. Further, the shape of each of the plurality of die pads may be a substantially right triangle, and one of the two sides sandwiching the right angle of the right triangle may be on the virtual extension of the support bar. With this configuration, the die pad is expanded in the coining step even in a direction in which the die pads do not approach each other, so that the risk of interference between the die pads due to the expansion is reduced. This eliminates the need to control the processing accuracy of the coining process severely.

On the other hand, according to the semiconductor device of the present invention,
The lead frame manufactured above, a semiconductor element fixed to a surface opposite to the main surface of the plurality of die pads, a bonding wire for electrically connecting an electrode terminal of the semiconductor element and the lead, A sealing body for sealing the main surface of the die pad. In this structure, since the die pad is covered with the sealing body and is not exposed to the outside of the semiconductor device, there is a risk that moisture may enter from between the die pad and the sealing body, and the design of the mounting substrate may be limited. There is nothing.

[0019]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1A and 1B are plan views showing a method for manufacturing a lead frame according to the present embodiment. First, as shown in FIG. 1A, a lead 12, a die pad 13, and a support bar 11 integrated with the die pad 13 are formed on a metal strip 10. This processing step is performed by punching with a press, and the metal strip 10 is made of, for example, copper.

As shown, the die pad 13 is divided into a plurality of pieces for each support bar 11 integrated therewith. The dividing step of dividing the die pad 13 may be performed simultaneously with the above-described processing step, or may be separately performed by pressing after the processing step. When they are performed simultaneously, there is an advantage that the manufacturing process is shortened. In the illustrated example, the shape of each of the plurality of die pads 13 is substantially rectangular, and one diagonal line 13 a of two diagonal lines of this rectangle is on a virtual extension of the support bar 11.

Thereafter, as shown in FIG. 1B, coining is performed on the coining area indicated by oblique lines. Here, a die (not shown) is pressed over the entire coining area, and the die pad 13 becomes thinner than the support bar 11. Since such coining is performed to reduce the thickness of the die pad 13, the coining region only needs to include all of the divided die pads 13.
Coining may be applied to the tip of the support bar 11.

The coining area is extended by the thickness reduced by the coining process. However, since the die pad 13 is already divided and separated from each other, the extension can be released to the space S between the die pads 13. Also, no distortion occurs in the support bar 11. Further, the present invention has an advantage that the manufacturing cost of the lead frame is reduced because the die pad 13 is made thinner by inexpensive coining processing, not by expensive half etching.

FIG. 1C is a cross-sectional view taken along the line AA of FIG. 1B. As shown in FIG.
The coining area having a thickness of 2 mm is thinned to about 0.05 to 0.10 mm by coining. However, this does not mean that the present invention is limited to this value. The thickness of the metal strip 10 and the working depth by coining may be arbitrarily set in consideration of various circumstances.

Further, in the example shown in FIG.
Of the two main surfaces 13c and 13d, a mold is pressed from one main surface 13c side, and coining is performed only on the one main surface 13c. In some cases, both main surfaces 13c and 13d are subjected to coining. May be subjected to coining. Thereafter, a known process such as plating a necessary portion is performed to complete the lead frame according to the present embodiment.

The method of dividing the die pad 13 is not limited to the above. If the die pad 13 is divided for each support bar 11, the die pad 13 may have an arbitrary shape, and may have a shape as illustrated in FIG. In the example of FIG.
The shape of each of the plurality of die pads 13 is substantially a right triangle, and two sides 13b, 1
One side 13b of 3e is substantially on the virtual extension of the support bar 11. Here, this “side 13b is“ substantially ”
It is on the virtual extension of the support bar 11, and FIG. FIG. 3 (b)
After the coining process, the die pad 1 shown in FIG.
3 is an enlarged plan view of FIG. As shown therein, the die pad 13 is extended by a coining process. And
Due to this extension, one side 13b of the die pad 13 is shifted from the virtual extension of the support bar 11. However, the shift amount is slight, and the one side 13b is located at a position close to the virtual extension, and is substantially “on” the virtual extension. That is, “the side 13b is“ substantially ”on the virtual extension of the support bar 11” does not mean that the side 13b must be exactly on the virtual extension of the support bar 11; This means that it may be shifted to some extent from the virtual extension.

By the way, the die pad 13 corresponds to FIG.
When the shape is a substantially right triangle as described above, there is an advantage that it is not necessary to control the processing accuracy of the coining process severely as compared with the shape shown in FIG.
This will be described with reference to FIG. FIG. 4 (a)
FIG. 1 shows a case where the shape of the die pad 13 is substantially rectangular.
This is nothing but the one shown in (b). In this case, the die pad 1 is moved in the direction of the arrow in the drawing by the coining process.
3 expands. As is clear from the figure, the die pad 13
Extend in directions approaching each other.

On the other hand, FIG. 4B shows a case where the die pad is a substantially right-angled triangle, which is nothing but the one shown in FIG. 3A. In this case, the die pad 13 is extended in the directions of arrows A, B, and C in the drawing by the coining process. Among these, arrows B and C indicate the extension in the direction in which the die pads 13 approach each other, while arrow A indicates the extension in the direction in which the die pads 13 do not approach each other. As described above, some of the extensions of the die pad 13 are in the direction in which the die pads 13 do not approach each other as indicated by the arrow A. This reduces the risk of the die pads 13 interfering with each other due to the extension, so that it is not necessary to control the processing accuracy of the coining process severely.

After the completion of the lead frame, the semiconductor device 14 shown in FIG.
To complete. FIG. 2A is a plan view of a semiconductor device 14 in which a semiconductor element 15 is mounted on a lead frame manufactured by the above manufacturing method. As shown in FIG. 2A, in the semiconductor device 14, the divided die pad 1
The semiconductor element 15 is fixed on the semiconductor device 3. This fixing is performed, for example, via a silver paste or the like.

FIG. 2B is a sectional view taken along the line BB of FIG. 2A. As shown in FIG. 2B, the electrode terminals (not shown) of the semiconductor element 15
Is electrically connected to the leading end of the lead 12 via The bonding wire 16 is made of, for example, a gold wire. The semiconductor element 15 and the bonding wire 16 are sealed by a sealing body 17 to prevent exposure to the outside air. The sealing body 17 is made of, for example, resin or ceramic.

Focusing on the lead 12, one main surface of the lead 12 is exposed on the back surface of the semiconductor device 14 without being bent. The exposed main surface serves as an external connection terminal of the semiconductor device 14. Due to these characteristics, the semiconductor device 14 is a so-called QFN type semiconductor device. However, of course, the present invention is not limited to the QFN type, and for example, a QFP (Quad Flat) may be used.
The present invention is also applicable to a (Package) type semiconductor device.

FIG. 2C is a sectional view taken along line CC of FIG. 2A. As shown in FIG.
Is fixed on the main surface 13d of the two main surfaces 13c and 13d of the die pad 13 which is not subjected to coining. Then, the main surface 13 c on the side subjected to coining is sealed by the sealing body 17 so that the die pad 13 is not exposed to the outside of the semiconductor device 14. This structure has an advantage that moisture does not enter from between the die pad 13 and the sealing body 17 and an advantage that it does not limit the design of a mounting board (not shown) such as a motherboard.

[0032]

As described above, according to the lead frame manufacturing method of the present invention, in the processing step, the lead, the die pad, and the plurality of support bars integrated with the die pad are formed in the metal strip. Formed. afterwards,
In the dividing step, the die pad integrally formed with the support bar is divided into a plurality of die pads separated from each other by dividing the die pad for each support bar. Thereafter, in a coining step, at least one main surface of each of the plurality of die pads is subjected to coining to reduce the thickness of the plurality of die pads.

According to this, even if the die pad is made thin in the coining step, the die pad is already divided and separated from each other, so that the expansion of the die pad can be released to the space between the die pads, and the distortion of the lead frame is reduced. It does not occur. In particular, when the shape of each of the plurality of die pads is substantially a right triangle and one of the two sides sandwiching the right angle of the right triangle is on the virtual extension of the support bar, the processing of the coining process is performed. There is no need to control the precision severely.

According to the semiconductor device of the present invention,
The lead frame manufactured as described above, a semiconductor element fixed to a surface opposite to the main surface of the plurality of die pads, a bonding wire for electrically connecting an electrode terminal of the semiconductor element and the lead, A sealing body for sealing the main surface of the die pad. In this structure,
Since the die pad is not exposed to the outside of the semiconductor device, there is no danger of moisture entering from between the die pad and the sealing body, and there is no restriction on the design of the mounting substrate.

[Brief description of the drawings]

1 (a) and 1 (b) are plan views showing a method for manufacturing a lead frame according to an embodiment of the present invention, and FIG. 1 (c) is a plan view of FIG. It is sectional drawing by the A line.

FIG. 2A is a plan view of a semiconductor device in which a semiconductor element is mounted on a lead frame manufactured by a lead frame manufacturing method according to an embodiment of the present invention, and FIG. 2) is a sectional view taken along line BB in FIG. 2A, and FIG. 2C is a sectional view taken along line CC in FIG. 2A.

FIG. 3A is a plan view in the case where the shape of the die pad is a substantially triangular shape, and FIG. 3B is an enlarged plan view of the roughly triangular die pad in the embodiment of the present invention. .

FIG. 4 is a plan view illustrating an advantage in a case where the shape of the die pad is substantially triangular in the embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Metal strip, 11 ... Support bar, 12, 31b ... Lead, 13, 31a ... Die pad, 13a ... Diagonal line, 13b, 13e ... Side, 13c, 13d: two main surfaces of die pad, 14, 30, 35, 36: semiconductor device, 15, 34: semiconductor element, 16, 32: bonding wire, 17, 33 ..Sealed body, 31: Lead frame, S: Space, R: Right angle.

Claims (8)

[Claims] A processing step of forming a lead, a die pad, and a plurality of support bars integrated with the die pad on a metal strip; and forming the die pad integrated with the support bar,
By dividing the support bar, a dividing step of dividing into a plurality of die pads separated from each other, and after the dividing step, a coining process is performed on at least one main surface of each of the plurality of die pads to form a coin. A coining step of reducing the thickness of the plurality of die pads. 2. The method according to claim 1, wherein the processing step and the dividing step are performed simultaneously. 3. In the dividing step, the shape of each of the plurality of die pads is roughly divided into rectangles, and one of two diagonals of the rectangle is on a virtual extension of the support bar. The method for manufacturing a lead frame according to claim 1 or 2, wherein: 4. In the dividing step, the shape of each of the plurality of die pads is divided into substantially right triangles, and one of two sides sandwiching a right angle of the right triangle is a virtual extension of the support bar. The method for manufacturing a lead frame according to claim 1, wherein the lead frame is located above. 5. A lead frame manufactured by the method for manufacturing a lead frame according to claim 1, and a semiconductor element fixed to a surface of the plurality of die pads opposite to a main surface thereof. A bonding wire for electrically connecting an electrode terminal of the semiconductor element to the lead; and a sealing body for sealing at least a main surface of the die pad. 6. A lead, a die pad divided into a plurality of pieces, and a plurality of support bars integrated with each of the divided die pads, wherein the die pad is thinner than the support bar. A lead frame. 7. The shape of each of the plurality of die pads is substantially rectangular, and one of two diagonals of the rectangle is on a virtual extension of the support bar. 7. The lead frame according to 6. 8. The shape of each of the plurality of die pads is a substantially right triangle, and one of two sides sandwiching a right angle of the right triangle is substantially on a virtual extension of the support bar. The lead frame according to claim 6, wherein: